1. Field of the Invention
The present invention relates to an inner-rotor-type motor, such as, for example, a stepping motor or the like, which includes a stator provided by winding a coil around a plurality of main poles as winding poles and a rotor arranged inside the stator.
2. Description of the Related Art
Conventionally, a stepping motor is used in a drive portion in a wide variety of fields including an information device field such as a printer, a facsimile machine, a copier or the like and an industrial device field such as a factory automation device or the like. In case where the stepping motor of this kind is, e.g., a hybrid type that makes use of a magnetic body and a permanent magnet as a rotor, there have been widely used inner-rotor-type motors disclosed in Japanese Patent Application Publication Nos. 2002-051528 and 2001-112521.
More specifically, a stator core is formed by installing a plurality of main poles in a core-back portion as a ring-shaped magnetic frame so as to protrude radially inward. A stator is formed by winding a coil around the respective main poles of the stator core through insulating members. A hybrid type rotor formed by interposing an axially-magnetized permanent magnet between a pair of magnetic bodies is arranged inside the stator with an air gap therebetween. Cover members are arranged at the axial opposite sides of the stator. A rotor shaft of the rotor is supported by bearings retained in the central portions of the cover members.
In the inner-rotor-type stepping motor of this configuration, the outer peripheral surface of the stator core, i.e., the outer peripheral surface of the core-back portion, forms a portion of an outer surface of the motor. It is therefore possible to effectively dissipate the heat generated within the motor through the stator core. Moreover, there is no need to cover the outer peripheral surface of the stator core with a motor cover. This provides an advantage in that it is possible to reduce the cost of materials such as a motor cover and the like. The cover members arranged at the axial opposite sides of the stator core are configured to wholly cover the coil and the insulating members protruding beyond the axial end surfaces of the stator core. For that reason, a dust-free interior of the motor is secured.
In the inner-rotor-type stepping motor mentioned above, when connecting the coil to an external device, as disclosed in, e.g., Japanese Patent Application Publication No. 2002-051528, an end portion of a coil and a drawing-out lead wire are connected to each other in a relay substrate arranged within a cover member. The lead wire is drawn out through an drawing-out hole formed in the cover member. Alternatively, as disclosed in, e.g., Japanese Patent Application Publication No. 2001-112521, an end portion of a coil is connected to a relay substrate arranged within a cover member. A connector is mounted to the relay substrate so that the connector can be electrically connected to the coil. The connector is led out through a portion of the cover member so that the connector can be connected to an external connector.
In the conventional configuration mentioned above, however, the drawing-out hole of the lead wire needs to be formed in the cover member in order to connect the coil to an external device. With a view to lead out the connector, the cover member needs to be subjected to special processing. This leads to an increase in the component processing cost. Moreover, the cover member needs to be fixed to the stator in an accurate fixing direction. This poses a problem in that the assembly becomes difficult.
While the foregoing description has been made by taking an instance where the motor employs a hybrid type rotor, the aforementioned problems are also posed in an inner-rotor-type motor that employs, as its rotor, a permanent magnet type rotor in which different magnetic poles are alternately arranged along a circumferential direction.